Flow indicator and apparatus for monitoring particles in air

ABSTRACT

A flow indicator includes a horizontally disposed housing having a lower inlet port drawing in an air sample, an interior space passing the air sample, an upper outlet port exhausting the air sample, and a transparent window allowing visual observation of at least a portion of the interior space. The flow indicator also includes a floater disposed within the housing to move vertically in response to the flow of the air sample to indicate a flow rate for the air sample, and a guide member extending upward from a lower portion of the housing and guiding movement of the floater.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of application Ser. No. 11/431,521,filed May 11, 2006. Of note, additional related divisional applicationsinclude [Attorney Docket No. SEC.1523D1] and [Attorney Docket No.SEC.1523D3].

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the invention relate to a flow indicator and an apparatusfor monitoring particles in air. More particularly, embodiments of theinvention relate to an apparatus adapted to draw an air sample from theair in a clean room and count particles contained in the air sample, anda flow indicator adapted to indicate the flow rate of the air sample.

2. Description of the Related Art

Semiconductor devices are commonly manufactured by performing a complexsequence of fabrication processes that form a number of semiconductordies, i.e., a number of electrical circuits individually formed onportions of a silicon wafer used as a substrate. Once the semiconductordies have been formed on a silicon wafer an electrical die sorting (EDS)process is performed which inspects the electrical characteristics ofthe electrical circuits formed by the sequence of fabrication processes.Thereafter, individual semiconductor dies are removed from the siliconwafer and packaged to form a competed semiconductor device. Thispackaging process generally involves encapsulating each semiconductordie in an epoxy resin.

The sequence of fabrication processes usually includes one or more of: adeposition process adapted to deposit a material layer on the substrate;a chemical mechanical polishing (CMP) process adapted to planarize amaterial layer; a photolithography process adapted to form a photoresistpattern, an etching process adapted to form a pattern having desiredelectrical characteristics from a material layer using the photoresistpattern; an ion implantation process adapted to selectively implant ionsinto specific regions of the substrate; a cleaning process adapted toremove impurities from the substrate; a drying process adapted to drycleaned substrate; an inspection process adapted to identify defects inthe material layer and/or the pattern; etc.

Many if not all of these fabrication processes are performed in aconventional clean room. Clean rooms are widely used to preventworkpieces, such as silicon wafers, from becoming contaminated byparticles in the air such as ordinary dust. The carefully controlledenvironment of a clean room is managed in accordance with variousdefined classes of cleanliness. Each clean room class is defined by theconcentration of contaminant particles and/or the largest acceptablediameter of contaminate particles allowable within the clean room.

Various measurement apparatuses have been developed to facilitate cleanroom management. A condensation particle counter, which is one suchmeasurement apparatus, operates under the principle that the particlesize increases during an alcohol evaporation process. An opticalparticle counter, which is another conventional measurement apparatus,measures the intensity of light scattered from a projected laser by theparticles in the sampled air.

Examples of particle monitoring apparatuses including such particlecounters are disclosed, for example, in Japanese Patent ApplicationPublication No. 8-054265, Korean Patent No. 252215, and U.S. Pat. No.5,856,623.

One conventional particle monitoring apparatus includes a sampling probeadapted to draw in an air sample, and a particle counter connected tothe sampling probe. The sampling probe is connected to the particlecounter by a sampling tube, and the vacuum pressure (i.e., a suctionforce) used to draw in the air sample in provided by a pump disposedwithin the particle counter. In the conventional particle monitoringapparatus, the flow rate of the air sample varies in accordance with thesuction force applied by the pump, the length of the sampling tube,leakage of the air sample throughout the apparatus, etc.

However, variations in the air sample flow rate cause problems in themanagement of clean room cleanliness. For example, when the air sampleflow rate falls abnormally low, the exact of contaminate particles inthe air cannot be accurately measured. Contamination of workpieces mayresult.

Thus, there is a need for an improved particle monitoring apparatus thatallows an air sample to be drawn into a particle counter at a constantflow rate. Such an apparatus will more readily facilitate acquisitionand evaluation of the air sample.

SUMMARY OF THE INVENTION

In one embodiment, the invention provides a flow indicator comprising; ahorizontally disposed housing comprising; a lower inlet port drawing inan air sample, an interior space passing the air sample, an upper outletport exhausting the air sample, and a transparent window allowing visualobservation of at least a portion of the interior space. The flowindicator also comprises a floater disposed within the housing to movevertically in response to the flow of the air sample to indicate a flowrate for the air sample, and a guide member extending upward from alower portion of the housing and guiding movement of the floater.

In a related embodiment, the guide member extends upward along a centralaxis of the housing, and the floater comprises a central hole throughwhich the guide member passes.

In another related embodiment, the floater comprises; an inner panelhaving the central hole, an outer tube extending downward from an outeredge portion of the inner panel and separated from an inner surface ofthe housing, and a guide tube extending downward from an inner portionof the inner panel and surrounding the guide member, wherein the guidetube guides the movement of the floater.

In another related embodiment, the flow indicator also comprises astopper disposed at an upper portion of the guide member and limitingrise height of the floater, or an exhaust pipe extending through theupper outlet port and exhausting the air sample.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the present invention will be described indetail hereinafter with reference to the accompanying drawings, in whichlike reference symbols refer to like or similar elements throughout. Inthe drawings:

FIG. 1 is a schematic view illustrating a particle monitoring apparatuscomprising a flow indicator in accordance with an exemplary embodimentof the present invention;

FIG. 2 is a cross-sectional view illustrating a sampling probe shown inFIG. 1 and the flow indicator shown in FIG. 1;

FIG. 3 is a perspective view illustrating a lower cap shown in FIG. 2;

FIG. 4 is a perspective view illustrating an upper cap shown in FIG. 2;

FIG. 5 is a perspective view illustrating a transparent tube shown inFIG. 2;

FIG. 6 is a perspective view illustrating a guide member and an exhaustpipe shown in FIG. 2;

FIG. 7 is a perspective view illustrating another exemplary embodimentof the lower cap shown in FIG. 3;

FIG. 8 is a perspective view illustrating yet another exemplaryembodiment of the lower cap as shown in FIG. 3;

FIG. 9 is a cross-sectional view illustrating a floater shown in FIG. 2;

FIG. 10 is a vertical cross-sectional view illustrating a flow indicatorin accordance with another exemplary embodiment of the presentinvention;

FIG. 11 is a horizontal cross-sectional view illustrating the flowindicator shown in FIG. 10;

FIG. 12 is a perspective view illustrating another exemplary embodimentof a lower cap shown in FIG. 10;

FIG. 13 is a perspective view illustrating yet another exemplaryembodiment of the lower cap shown in FIG. 10;

FIG. 14 is a vertical cross-sectional view illustrating a flow indicatorin accordance with yet another exemplary embodiment of the presentinvention;

FIG. 15 is a horizontal cross-sectional view illustrating the flowindicator shown in FIG. 14;

FIG. 16 is a perspective view illustrating a floater shown in FIG. 14;and

FIG. 17 is a schematic view illustrating a particle monitoring apparatusin accordance with still another exemplary embodiment of the presentinvention.

DESCRIPTION OF EMBODIMENTS

As used herein, the term “and/or” includes any and all combinations ofone or more of the associated listed items.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, these elements should notbe limited by these terms. These terms are only used to distinguish oneelement from another. For example, a first thin film could be termed asecond thin film, and, similarly, a second thin film could be termed afirst thin film without departing from the teachings of the disclosure.

The terminology used herein is used only for the purpose of describingparticular embodiments of the invention and is not intended to limit theinvention.

Furthermore, relative terms, such as “lower” or “bottom” and “upper” or“top,” may be used herein to describe one element's relationship toanother element or other elements illustrated in the drawings. It willbe understood that relative terms are intended to encompass differentorientations of an element in addition to the orientation depicted inthe drawings. For example, if a first element in one of the drawings isturned over, secondary elements described as being on the “lower” sidethe first element would then be oriented on “upper” side of the firstelement. Therefore, the exemplary term “lower” can encompasses both anorientation of “lower” and “upper,” depending of the particularorientation of one or more elements in the drawing. Similarly, if afirst element in one of the drawings is turned over, secondary elementsdescribed as “below” or “beneath” the first element would then beoriented “above” the first element. Therefore, the exemplary terms“below” or “beneath” can encompass both an orientation of above andbelow.

Embodiments of the present invention are described herein with referenceto cross-sectional illustrations that are schematic illustrations ofidealized embodiments of the present invention. As such, variations fromthe shapes shown in the illustrations as a result of, for example,manufacturing techniques and/or tolerances, are to be expected. Thus,embodiments of the present invention should not be construed as beinglimited to the particular shapes of regions illustrated herein, but areto include deviations in shapes that result from, for example,manufacturing. For example, a region illustrated or described as flatmay, typically, have rough and/or nonlinear features. Moreover, sharpangles illustrated in the drawings may be rounded. Thus, the regionsillustrated in the drawings are schematic in nature and their shapes arenot intended to illustrate the precise shape of a region and are notintended to limit the scope of the present invention.

FIG. 1 is a schematic view illustrating a particle monitoring apparatuscomprising a flow indicator in accordance with an exemplary embodimentof the present invention.

Referring to FIG. 1, a particle monitoring apparatus 10 may be used tomonitor the inner environment of a clean room in which semiconductordevices are manufactured. Particularly, particle monitoring apparatus 10may be used to measure the concentration of particles in a primary airsample taken from the interior of a clean room.

The primary air sample may comprise a first air sample drawn by asampling probe 12 and a second air sample drawn by a flow indicator 100coupled to sampling probe 12. In more detail, sampling probe 12 isdisposed in a clean room and draws the first air sample. Flow indicator100 is coupled vertically to sampling probe 12 and draws the second airsample. An “entire flow rate” associated with the first and second airsamples may be determined on the basis of the ascertained flow rate forthe second air sample.

A particle counter 14 may be connected to sampling probe 12 by asampling tube 16. Although not shown in detail in the drawings, particlecounter 14 may comprise a laser optical member adapted to detect theparticles in the primary air sample and a pump adapted to provide thesuction force necessary to draw in the primary air sample.Alternatively, particle monitoring apparatus 10 may comprise acondensation particle counter.

FIG. 2 is a cross-sectional view illustrating sampling probe 12 and flowindicator 100 shown in FIG. 1.

In the illustrated example, sampling probe 12 has a funnel shape and isusually intended to be mounted or disposed in a horizontal manner (e.g.,relative to a wall of the clean room). Assigning a horizontalorientation to sampling probe 12, flow indicator 100 is coupledsubstantially vertically to a lower portion of sampling probe 12.

Flow indicator 100 may Comprise a housing 110 that has an interior space110 a, which is used as a flow passage for the second air sample, and afloater 120 disposed in interior space 11 a. Housing 110 has acylindrical shape and is disposed in a vertical direction. Further,housing 110 has a plurality of lower inlet ports 110 b, through whichthe second air sample is drawn into flow indicator 100, and an upperoutlet port 110 c, through which the second air sample that passesthrough interior space 110 a is exhausted into sampling probe 12.Housing 110 also comprises a transparent window 110 d, through whichinterior space 110 a may be observed. Floater 120 may move in thevertical direction within housing 110 in accordance with the flow of thesecond air sample through interior space 110 a.

Additionally, housing 110 may comprise a lower cap 112 having theplurality of lower inlet ports 110 b, an upper cap 114 having upperoutlet port 110 c, and a transparent tube 116 coupled between lower andupper caps 112 and 114 and which serves as transparent window 110 d.Transparent tube 116 is inserted into lower and upper caps 112 and 114with an interference fit to prevent the second air sample from leakingout of housing 110 once it has been drawn into interior space 110 a.

Guide member 130 is disposed inside of housing 110 and guides themovement of floater 120. Guide member 130 extends upwardly from a lowerportion of housing 110. In more detail, guide member 130 extendsupwardly from a lower central portion of housing 110 along a centralaxis of housing 110, and floater 120 has a central hole through whichguide member 130 passes. In addition, a ring-shaped stopper 132 isdisposed at an upper portion of guide member 130 to limit the height towhich floater 120 may rise (i.e., to keep floater 120 from moving to apoint above stopper 132).

The second air sample drawn through the plurality of lower inlet ports110 b flows from a lower portion of interior space 110 a into an upperportion of interior space 110 a through a gap between housing 110 andfloater 120, and is then exhausted into sampling probe 12 through anexhaust pipe 140 extending through upper outlet port 110 c.

Exhaust pipe 140 has a plurality of holes 140 a through which the secondair sample is drawn in order to exhaust the second air sample after thesecond air sample has flowed into the upper portion of interior space110 a. Holes 140 a are formed radially around a lower portion of exhaustpipe 140. In the illustrated example shown in FIGS. 2 and 6, exhaustpipe 140 is disposed coaxially with guide member 130, and exhaust pipe140 and guide member 130 are formed as one linear piece. However, guidemember 130 and exhaust pipe 140 may be provided separately.

Sampling probe 12 has a coupling hole 12 a formed through a lowerportion of sampling probe 12, and exhaust pipe 140 is coupled inside ofcoupling hole 12 a with an interference fit, thereby coupling flowindicator 100 with sampling probe 12. When flow indicator 100 andsampling probe 12 are coupled in this manner, sealing members 150 may beinterposed between coupling hole 12 a and exhaust pipe 140 to preventleakage of the first and second air samples. For example, O-rings may beinterposed between coupling hole 12 a and exhaust pipe 140, and whenO-rings are interposed between coupling hole 12 a and exhaust pipe 140,flow indicator 100 is fixed to sampling probe 12 by the O-rings.Further, a fixing clip 152 may be disposed at exhaust pipe 140 to limitthe position at which exhaust pipe 140 may be coupled to housing 110.

FIGS. 3, 4, and 5 are perspective views illustrating lower cap 112,upper cap 114, and transparent tube 116, respectively, each of which isshown in FIG. 2. FIG. 6 is a perspective view illustrating guide member130 and exhaust pipe 140 as shown in FIG. 2.

Referring to FIGS. 3 through 6, lower cap 112 has a cylindrical shapeand has a closed lower end and an open upper end (i.e., the lower end iscovered by a lower panel 112 a, while the upper end is not covered). Onthe contrary, upper cap 114 has a cylindrical shape and has a closedupper end and an open lower end (i.e., the upper end of upper cap 114 iscovered by an upper panel 114 a, while the lower end is not covered).

Particularly, lower cap 112 comprises lower panel 112 a, and a lowertube 112 b extending upwardly from lower panel 112 a and having a firstlength in a direction perpendicular to lower panel 112 a. Also, lowerpanel 112 a has the plurality of lower inlet ports 110 b. Upper cap 114comprises upper panel 114 a, and an upper tube 114 b extendingdownwardly from the upper panel 114 a and having a second length in adirection perpendicular to upper panel 114 a. Also, upper panel 114 ahas upper outlet port 110 c.

Lower inlet ports 110 b are arranged radially around the center of lowerpanel 112 a. Lower inlet ports 110 b may be arranged at regularintervals along a circle concentric to the circumference of lower panel112 a as desired. Though four lower inlet ports 110 b are arrangedradially around the center of lower panel 112 a shown in FIG. 3, thescope of the present invention is not limited by the number of lowerinlet ports 110 b shown in FIG. 3.

A threaded hole 112 c is formed through a central portion of lower cap112. Threaded hole 112 c is used to couple lower cap 112 to guide member130, and guide member 130 has a threaded end portion 134 that isthreadably engaged with threaded hole 112 c. As shown in the drawings,guide member 130 has a circular horizontal cross-section. However, guidemember 130 may have a polygonal horizontal cross-section to preventfloater 120 from rotating.

Transparent tube 116 is provided so that the movement of floater 120 ininterior space 110 a, which is caused by the flow of the second airsample, may be observed visually. Transparent tube 116 has a thirdlength along a central axis of transparent tube 116 that is longer thanthe sum of the first length of lower tube 112 b and the second length ofupper tube 114 b so that floater 120 in interior space 110 a may beobserved. Transparent tube 116 also has an inner diameter that isconstant along the third length so that floater 120 will move stablywithin transparent tube 116. Furthermore, transparent tube 116 maycomprise outer step portions (i.e., the upper and lower portions oftransparent window 110 d of FIG. 5) that bound the respective positionsat which each of lower and upper caps 112 and 114 may be coupled totransparent tube 116, as shown in FIGS. 2 and 5.

Exhaust pipe 140 and guide member 130 are provided in one piece. Aplurality of first annular grooves 140 b is formed in an upper portionof exhaust pipe 140, and a sealing member 150 (of FIG. 2) is mounted ineach of the plurality of first annular grooves 140 b. A second annulargroove 140 c is formed adjacent to the plurality of first annulargrooves 140 b, and fixing clip 152, which limits the position at whichguide member 130 and exhaust pipe 140 may be coupled to housing 110, ismounted in second annular groove 140 c.

FIGS. 7 and 8 are perspective views illustrating other exemplaryembodiments of lower cap 112 of FIGS. 2 and 3.

Referring to FIG. 7, a lower cap 160 may comprise a lower panel 162,which has a plurality of fine inlet ports 162 a uniformly formed inlower panel 162 and used to draw the second air sample into inner space110 a, and a lower tube 164 that extends upwardly from lower panel 162.In addition, lower panel 162 has a threaded hole 162 b in a centralportion of lower panel 162 by which lower cap 160 is coupled to guidemember 130.

Referring to FIG. 8, a lower cap 170 may comprise a lower panel 172having eight lower inlet ports 172 a formed in lower panel 172, arrangedat regular intervals along a circle concentric to the circumference oflower panel 172, and used to draw the second air sample into interiorspace 110 a; and lower cap 170 may further comprise a lower tube 174that extends upwardly from lower panel 172. Further, lower panel 172 hasa threaded hole 172 b in a central portion of lower panel 172 by whichlower cap 170 is coupled to guide member 130. Each lower inlet port 172a has a diameter smaller than the diameter of each lower inlet port 110b of FIG. 3.

Referring to FIGS. 3, 7, and 8, the number of inlet ports 110 b, 162 a,and 172 a formed in lower cap 112, 160, and 170, respectively, may vary.However, an entire cross-sectional area of inlet ports 110 b, 162 a, or172 a may be determined in accordance with the normal entire flow rateof the primary air sample, and the number and diameter of the inletports 110 b, 162 a, or 172 a may be adjusted in accordance with thenormal range of the entire flow rate of the primary air sample. Forexample, when the normal entire flow rate of the primary air sampleranges from about 4 to about 9 l/min, each of the lower inlet ports 110b (of FIG. 3) may have a diameter of about 4 mm.

FIG. 9 is a cross-sectional view illustrating floater 120 of FIG. 2.

Referring to FIG. 9, floater 120 may comprise an inner panel 122, anouter tube 124, and a guide tube 126. Inner panel 122 has a disk shape,and guide member 130 passes through a central hole formed in a centralportion of inner panel 122. Outer tube 124 extends downwardly from anouter edge portion of inner panel 122 and the outer surface of outertube 124 faces an inner surface of transparent tube 116. Guide tube 126extends downwardly from an inner portion of inner panel 122 andsurrounds guide member 130 so that guide member 130 may guide themovement of floater 120 caused by the flow of the second air sample.

A first gap between guide tube 126 and guide member 130 is less than orequal to about 0.1 mm so that the second air sample can be restrainedfrom flowing through the first gap. For example, the first gap betweenguide tube 126 and guide member 130 may be about 0.05 mm. A second gapbetween outer tube 124 and transparent tube 116 may be determined inaccordance with the normal entire flow rate of the primary air sample.For example, when the normal entire flow rate of the primary air sampleis about 4 to about 9 l/min, and an outer diameter of outer tube 124 isabout 25 to about 26 mm, the second gap may be about 0.3 to about 0.5mm.

Outer tube 124 may comprise a plurality of tubes, wherein each tube ofthe plurality of tubes is a different color in order to facilitatevisual observation of the movement of floater 120 through transparenttube 116. Particularly, outer tube 124 comprises a first color tube 124a that extends downwardly from the outer edge portion of inner panel 122and has a first color, and a second color tube 124 b that is coupled toa lower end of first color tube 124 a and has a second color differentfrom the first color. For example, the first color and the second colormay be red and blue, respectively. Step portions are formed at the lowerportion of first color tube 124 a and an upper portion of the secondcolor tube 124 b in order to provide an interference fit between firstand second color tubes 124 a and 124 b.

The flow of the second air sample moves floater 120 vertically withininterior space 110 a, and the flow rate of the second air sample isascertained by observing the position of floater 120 through transparenttube 116. For example, when the primary air sample is drawn at a normalflow rate, the second color of floater 120 (e.g., blue) will be visiblethrough transparent tube 116. On the contrary, when the first color offloater 120 (e.g., red) is visible through transparent tube 116, theprimary air sample is not being drawn at a normal flow rate. That is,when the flow rate of the second air sample is reduced below a normalflow rate, the first color of floater 120 is visible through transparenttube 116 because floater 120 has, as a result of the reduced flow rateof the second air sample, a lower position within interior space 110 athan it has when the second air sample is being drawn at a normal flowrate for the second air sample. Particularly, when the second color offloater 120 is observed through transparent tube 116, the primary airsample has an entire flow rate of about 4 to about 9 l/min and is beingdrawn normally. When the first color of floater 120 is observed throughtransparent tube 116, the primary air sample has an entire flow rate ofless than or equal to about 1 l/min and is being drawn abnormally.Further, when the first and second colors of floater 120 are observedthrough transparent tube 116 at the same time, the primary air sample isbeing drawn at an entire flow rate of about 2 to about 3 l/min.

The position of floater 120 can be easily observed with the naked eye byobserving the color(s) of floater 120 visible through transparent tube116. So, even when sampling probe 12 and flow indicator 100 are disposedadjacent to a ceiling of the clean room, an operator can easilyascertain whether or not the primary air sample is being drawn normally.

FIG. 10 is a vertical cross-sectional view illustrating a flow indicatorin accordance with another exemplary embodiment of the presentinvention, and FIG. 11 is a horizontal cross-sectional view illustratingthe flow indicator shown in FIG. 10. FIGS. 12 and 13 are perspectiveviews illustrating exemplary embodiments of the lower cap shown in FIG.10.

Referring to FIGS. 10 and 11, a flow indicator 200, in accordance withan exemplary embodiment of the present invention, may comprise acylindrical housing 210 comprising an interior space 210 a and a floater220 disposed within housing 210 and which may move vertically withinhousing 210.

Flow indicator 200 is coupled to a lower portion of a sampling probethat draws a first air sample. In addition, flow indicator 200 comprisesa lower cap 212 having a plurality of lower inlet ports 210 b throughwhich a second air sample is drawn, an upper cap 214 having an upperoutlet port 210 c through which an exhaust pipe 240 is inserted, whereinexhaust pipe 240 is adapted to exhaust the second air sample, and atransparent tube 216 coupled between lower and upper caps 212 and 214.

Though lower cap 212 of FIG. 11 has four lower inlet ports 210 b throughwhich the second air sample may be drawn, the scope of the presentinvention is not limited by the number of lower inlet ports 210 b shownin FIG. 11. For example, a lower cap 260 (shown in FIG. 12) may have aplurality of fine lower inlet ports 260 a formed uniformly in lower cap260, and a lower cap 270 (shown in FIG. 13) may have one lower inletport 270 a. Lower caps 260 and 270 are each alternate exemplaryembodiments of lower cap 212 of flow indicator 200 of FIGS. 10 and 11.

Referring again to FIGS. 10 and 11, transparent tube 216 comprises aplurality of rails 230 that protrude from an inner surface oftransparent tube 216 and extending substantially vertically to guide themovement of floater 220.

Floater 220 comprises an inner panel 222 that has the shape of a diskand is disposed in a direction substantially perpendicular to a centralaxis of housing 210, and an outer tube 224 that extends downwardly froman outer edge portion of inner panel 222. Outer tube 224 is separatedfrom the inner surface of transparent tube 216, and a plurality of guidegrooves 224 a is formed in the outer surface of outer tube 224. Theplurality of guide grooves 224 a is adapted to engage with the pluralityof rails 230. As an example, when (1) the entire flow rate of the firstand second air samples is about 4 to about 9 l/mm, (2) each of the fourlower inlet ports 210 b has an inner diameter of about 4 mm, and (3) theouter diameter of outer tube 224 is about 25 to about 26 mm, then thegap between outer tube 224 and transparent tube 216 may be about 0.3 toabout 0.5 mm. Further, the gap between each rail 230 and itscorresponding guide groove 224 a may be less than or equal to about 0.1mm.

Outer tube 224 comprises a first color tube 226 that extends downwardlyfrom the outer edge portion of inner panel 222 and has a first color,and a second color tube 228 that is coupled to a lower end of firstcolor tube 226 and has a second color different from the first color.

Each stopper 232 of a plurality of stoppers 232 is disposed on a rail230 of the plurality of rails 230 to limit the height to which floater220 may rise.

Exhaust pipe 240 extends through upper outlet port 210 c of upper cap214, and a lower end of exhaust pipe 240 is disposed higher than each ofthe plurality of stoppers 232. As shown in FIG. 10, exhaust pipe 240comprises an open upper end, a closed lower end, and a plurality ofholes 240 a that are formed radially around a lower portion of exhaustpipe 240 and through which the second air sample is drawn out of housing210. However, exhaust pipe 240 may have an open lower end.

Many of the elements of flow indicator 200 are similar or identical tothose already described regarding flow indicator 100 shown in FIGS. 1through 9, so further detailed description of those elements will beomitted herein.

FIG. 14 is a vertical cross-sectional view illustrating a flow indicatorin accordance with yet another exemplary embodiment of the presentinvention, FIG. 15 is a horizontal cross-sectional view illustrating theflow indicator shown in FIG. 14, and FIG. 16 is a perspective viewillustrating a floater shown in FIG. 14.

Referring to FIGS. 14 through 16, a flow indicator 300, in accordancewith an exemplary embodiment of the present invention, may comprise acylindrical housing 310 comprising an interior space 310 a and a floater320 disposed within housing 310 and which may move vertically withinhousing 310.

Flow indicator 300 is coupled substantially vertically to a lowerportion of a sampling probe adapted to draw a first air sample. Housing310 may comprise a lower cap 312 having a plurality of lower inlet ports310 b through which a second air sample may be drawn. Housing 310 mayalso comprise an upper cap 314 having an upper outlet port 310 c throughwhich an exhaust pipe 340, which is adapted to exhaust the second airsample into the sampling probe, is disposed, and a transparent tube 316coupled between lower and upper caps 312 and 314.

Transparent tube 316 comprises a plurality of rails 330, which protrudefrom an inner surface of transparent tube 316, extend substantiallyvertically, and which are adapted to guide the vertical movement offloater 320.

Floater 320 may comprise an inner panel 322 disposed in a directionsubstantially perpendicular to a central axis of housing 310. Innerpanel 322 may have a plurality of first holes 322 a through which thesecond air sample may pass. Floater 320 may further comprise an outertube 324 that extends downwardly from an outer edge portion of innerpanel 322 and comprises a plurality of guide grooves 324 a adapted toengage with the plurality of rails 330. A first gap between outer tube324 and transparent tube 316 may be less than or equal to about 0.1 mm.Also, one of a plurality of second gaps is formed between each rail 330and its corresponding guide groove 324 a. Each of the plurality ofsecond gaps may be less than or equal to about 0.1 mm.

Outer tube 324 comprises a first color tube 326 that extends downwardlyfrom the outer edge portion of inner panel 322 and has a first color,and a second color tube 328 that is coupled to a lower end of firstcolor tube 326 and has a second color different from the first color.

Flow indicator 300 also comprises a plurality of stoppers 332. Each ofthe plurality of stoppers 332 is disposed on a rail 330 of the pluralityof rails 330 to limit the height to which floater 320 may rise.

Exhaust pipe 340 extends through upper outlet port 310 c of upper cap314, and a lower end of exhaust pipe 340 is disposed higher than each ofthe plurality of stoppers 332. As shown in FIG. 14, exhaust pipe 340comprises an open upper end, a closed lower end, and a plurality ofsecond holes 340 a that are formed radially around a lower portion ofexhaust pipe 340 and through which the second air sample may be drawnout of housing 310. However, exhaust pipe 340 may have an open lowerend.

Many of the elements of flow indicator 300 are similar or identical tothose already described regarding flow indicator 100 shown in FIGS. 1through 9 or flow indicator 200 shown in FIGS. 10 through 13, so furtherdetailed description of those elements will be omitted herein.

FIG. 17 is a schematic view illustrating a particle monitoring apparatusin accordance with still another exemplary embodiment of the presentinvention.

Referring to FIG. 17, a particle monitoring apparatus 20, in accordancewith an exemplary embodiment of the present invention, may comprise aplurality of sampling probes 22 located in several places in a cleanroom and a plurality of flow indicators 400, each of which is coupled toa sampling probe 22 of the plurality of sampling probes 22. Eachsampling probe 22 is adapted to draw a primary air sample and each flowindicator 400 is adapted to indicate the flow rate of the primary airsample.

Each sampling probe 22 is connected to a manifold 26 by one of aplurality of sampling tubes 24. Manifold 26 is connected by a suctiontube 30 to a first pump 28 adapted to draw the primary air samples. Inaddition, manifold 26 is connected by a second sampling tube 34 to aparticle counter 32 adapted to count particles in the primary airsamples. In particular, manifold 26 is adapted to selectively providethe primary air samples drawn from the locations of sampling probes 22to particle counter 32. Particle counter 32 may comprise a laser opticalmember adapted for use in counting particles contained in the selectedprimary air sample, and may also comprise a second pump adapted to drawthe selected air sample into particle counter 32.

Further detailed descriptions of sampling probes 22 and flow indicators400 will be omitted because each of sampling probes 22 and flowindicators 400 is similar or identical to sampling probes and flowindicators, respectively, that have already been described in connectionwith previously described exemplary embodiments of the presentinvention.

In accordance with exemplary embodiments of the present invention, anair sample is provided to the particle counter to measure the degree ofcontamination of the clean room. The flow rate of the air sample may beeasily ascertained by observing the floater through the transparenttube; and thus, the reliability of a measurement of the degree ofcontamination of the clean room taken by the particle counter may beimproved.

Further, the flow rate of the air sample may be observed visually at anytime. Thus, there is no need to separately check the operation of theparticle monitoring apparatus, and the time required check the operation(or operating state) of the particle monitoring apparatus may bereduced. Consequently, the cleanliness of the clean room may bemaintained constantly. Furthermore, deterioration in the cleanliness ofthe clean room caused by variation in the flow rate of the air samplesmay be prevented.

Although exemplary embodiments of the present invention have beendescribed herein, the present invention is not limited to the exemplaryembodiments described. Rather, those skilled in the art will recognizethat various changes and modifications can be made to the exemplaryembodiments while remaining within the scope of the present invention asdefined by the following claims.

1. A flow indicator comprising: a horizontally disposed housingcomprising: a lower inlet port drawing in an air sample; an interiorspace passing the air sample; an upper outlet port exhausting the airsample; and, a transparent window allowing visual observation of atleast a portion of the interior space; a floater disposed within thehousing to move vertically in response to the flow of the air sample toindicate a flow rate for the air sample; and a guide member extendingupward from a lower portion of the housing and guiding movement of thefloater.
 2. The flow indicator of claim 1, wherein the guide memberextends upward along a central axis of the housing, and the floatercomprises a central hole through which the guide member passes.
 3. Theflow indicator of claim 2, wherein a plurality of lower inlet ports isdisposed radially around a center of the lower portion of the housing.4. The flow indicator of claim 2, wherein the floater comprises: aninner panel having the central hole; an outer tube extending downwardfrom an outer edge portion of the inner panel and separated from aninner surface of the housing; and, a guide tube extending downward froman inner portion of the inner panel and surrounding the guide member,wherein the guide tube guides the movement of the floater.
 5. The flowindicator of claim 4, wherein the outer tube comprises: a first colortube having a first color, the first color tube extending downward fromthe outer edge portion of the inner panel; and, a second color tubehaving a second color different from the first color, the second colortube being coupled to a lower end of the first color tube.
 6. The flowindicator of claim 4, wherein a gap between the guide tube and the guidemember is less than about 0.1 mm.
 7. The flow indicator of claim 2,further comprising: a stopper disposed at an upper portion of the guidemember and limiting rise height of the floater.
 8. The flow indicator ofclaim 2, further comprising: an exhaust pipe extending through the upperoutlet port and exhausting the air sample.
 9. The flow indicator ofclaim 8, wherein the exhaust pipe and the guide member are formed as asingle piece; and, a plurality of holes is formed radially around alower portion of the exhaust pipe disposed within the housing, whereinthe housing exhausts the air sample through the plurality of holes.